The Contractor will receive, maintain, and expand cell lines and virus for use in testing experimental agents against the HIV virus, prepare experimental agents for testing, test for antiviral activity of 10,000 agents per year in accordance with NCI approved protocol for large scale HIV Screening, and submit testing results as specified. The Contractor will also perform confirmation testing on approximately 80 experimental agents per year identified as active in the primary screen, conduct more detailed testing of 30 to 40 experimental agents per year, and maintain a pathogen free mouse facility for testing of experimental agents in a small animal model system.